On old 028WB, the tank vent originally was two fine treaded inserts specifically located. These would allow for tank pressure to equalize. The newer vents seem to only allow air to pull into the tank to eliminate a vacuum. Are the older original carbs incompatible with the newer vent function as the tank pressure can get quite high and put a lot of fuel pressure and possibly more volume into the carb per each sequence of the needle opening,
Be careful with some of the Echo trimmers in the line where the fuel vent is there is a small white filter if it is restricted in any way it will starve the fuel system I know this because we had one at the dealership here that was partially plugged and it would starve the engine of fuel after running for like 45 minutes it was extremely hard to diagnose
I think this is why my Scag Turf Tiger 29hp DFI to cut out. I haven't check it yet because I just found your video but thank you very much. I'm sure this helped a lot of people.
Had a faulty tank vent on a BR340, replaced it with an OEM one but was still having fuel starvation issues, installed an Echo one and it hasn't given him any trouble since
I pressure test the tanks and fuel lines in chainsaws the same way. I plug my Mighty Vac into the fuel line going to the carb and pump it up to 7#. It better hold. If it holds, I switch it to vacuum and pump it up. It should gradually release. If it does not hold pressure, there could be a leak in the fuel line, tank, tank cap or a bad tank vent. I start looking for the leak with spray soapy water.
Or if it dies after a carb rebuild or replacement you can always just unscrew the cap, re prime and try it with the cap off, if it runs fine without the cap then its a vent issue
I test my gas tank with my Mighty Vac. I plug it into the fuel line going into the tank. It should pressure up to 7# and hold at that pressure. If it does not pressure up, there is a leak, somewhere. I will use a spray soapy water mixture to find the leak. If a tank does not hold pressure when the gas gets hot it will boil in the tank and cause a lean condition in the saw. After it passes the pressure test, I switch to vacuum and pump it up to 7-10 inches of vacuum. It should gradually reduce to zero inches of vacuum as the tank vent allows outside air in. If the tank vent does not work correctly, the carburator will not be able to pump gas against the vacuum in the tank. You will also hear a “who’s” when you open the gas tank.
Thanks i never knew thet the tank pressure or vent was important !! Or what acures when its not right ! Got a few old saws that will visibly leak fuel from vent ! Still use them when needed always figured saw isn't quite working right but just put it down to been a old tired machine!! Got to get myself one of them pressure/ vacuum testing gadgets and give the old veterans some tlc
I pressure cheviot my complete fuel system to 7# and 7inches of vacuum. I pressure check carbs to 5# and 5 inches of vacuum. I check engines to 7# and 7 inches vacuum. The Stihl service manual says they can drop one pound per minute but cannot drop below 4#.
@@THEMOWERMEDIC1 you won’t get it on an ms 440 or 360. You get a gradual leak down to 4#. This is because the oil pump spacer plugs into the pto side seal. Husqvarna has a recess on the 372 where they install a small O ring but Stihl does not and you will get a little pressure loss. I talked with my local Stihl tech and he told me the spec and my 440 passed that spec. He told me not to worry about it. On the 440 the pressure loss is between the spacer’s inside dimension and the crank It does not leak around the seal. I sprayed it good with soapy water and got no leaks. As the saw warms up and the clutch and oil pump are screwed down this little leak probably also stops.
I have an almost new BR800 Stihl backpack blower and when I started it the other day and got to full throttle okay but then after just a few seconds it started to die like it is out of gas. Three or four quick blips of the throttle and it would rev back up but a few seconds later would start to die again. I was sure it wasn’t the gas but dumped it even though it wasn’t that old but it made no difference. It idles fine and I checked several things I was sure it wasn’t and was right so was wondering if you think it may be the fuel tank vent?
Was just riding my 1996 GL1500 GoldWing. Late night, heading home through a wooded desolate park. Motor was fine and always has been . Just criusing along and withno warning, motor bogged and then died. I pulled over and thought what to do. (Tank was full and I knew it for sure, because I'd filled out last night before garaging. I cranked and wouldn't start but did try Then set full come and it did eventually start. Futzed with throttle and come and got it running again. Staked 5min later. Starting was getting battery drained but got it, drove out of woods. Still thinking "what the hell"? Rinse repeat a few more times. Few miles/ stalls later, I got to gas station. Got carb cleaner and a half gallon of gas to confirm and get fresh. I had begun to think, "what changed and what could I have done when I fuels last night?". "Gas cap? Fuel line? Vent line?". Sure uff, opened fuel door and I had thought looked the vent line. So finished riding home. WOT, anything, didn't have problem going last 8 miles. So, I figured, UA-cam up some vids on the vent line and stallinng. 3rd vid was this and near the end, you confirmed not only the effect of vent line "clogging" but also, that is gotten my 30 miles ok riding since filling track last night.
I'm hoping you can help me with a Bad Boy Maverick zero turn problem. The fuel line from the tank to the fuel pump will not pick up fuel. But if i remove the line from the fitting and put it down in the tank it will pick up the fuel and start. I have installed a new fuel pump and all new fuel filters. The man that owns this mower told me he had try to remone the fuel line inside the tank and couldn't get it out and may have damaged something there. Any info would be appreciated.
So would it cause my engine to shut off after running for about 10 minutes? Then also make it hard to restart I have to let it sit for a few minutes before I can restart.
So via the stihl technical it says ti check the valve with gas cap on and the inlet plugged and vacuum pump hooked to return. It says there should be no vacuum build up and should hold pressure. Thats the opposite of what you say in the beginning. Im a little confused.
Is a symptom of a bad valve a LOT of vacuum release when I remove the gas cap? I'm having runnability issues on my FS131 Stihl trimmer and it bogs out, loses power, then its hard to keep running. Opening the gas cap and WHOOSH, TF is that?.. I replaced the spark plug, fuel filter, air filter and just run MotoMix. Should I just replace the valve? I don't have the fancy pressure gauge testy.
so i’m have a problem with some stihl weed eaters the vents keep going bad, I put a new on on it runs for a few weeks then the vent fails. what might cause that?
I have a John Deere 345 r zero turn . I can’t get fuel into the tank . I have to sit for a min and keep adding gas . It always acts full but I have to keep adding fuel . Do you know why that would occur ? I’ve watched 80 videos and nothing addresses this problem . The mower is off and I have to keep adding gas ? Help , please
pardon my question here, sometimes I'm a little slow. So i'm having issues with my Stihl FS91R like it is starving for gas, at 1st it only did this when the motor got hot, now it will not run longer then 30 seconds. When I remove the gas cap I get woosh of air, believe it is vacuum lock. Don't have compression tester but would this be a sign of tank vent needing replacement. Thanks for your teaching work. Tim N
My gravely pro turn 152 gas tanks make a intermittent whistling sound throughout the day when it's hot. Is it the gas caps causing this or is it normal for it to do this?
Do you know this issue of a Stihl not wanting to start especially after running for awhile and being stopped for a bit. or when the temperature goes up into the 30's or machine is sitting in the sun. Is this something to do with the vent of fuel circuit? Has something to do with heat and fuel/vapour. usually have to prime it then but that isn't enough. Something that helps is I have to hold throttle while starting.
All my Stihl machines do this. Every single one. The 4 mix ones (KM131R) are the worst for this. Yes throttle fully open helps. Sometimes I have to remove the spark plug and manually deflood it. I also keep them in the shade when on site so they stay cool and also, NEVER store upside down! always upright :)
These machines are great at what they do ,but they are finicky at the same time ,old jimmy follow you from Australia
On old 028WB, the tank vent originally was two fine treaded inserts specifically located. These would allow for tank pressure to equalize. The newer vents seem to only allow air to pull into the tank to eliminate a vacuum. Are the older original carbs incompatible with the newer vent function as the tank pressure can get quite high and put a lot of fuel pressure and possibly more volume into the carb per each sequence of the needle opening,
Be careful with some of the Echo trimmers in the line where the fuel vent is there is a small white filter if it is restricted in any way it will starve the fuel system I know this because we had one at the dealership here that was partially plugged and it would starve the engine of fuel after running for like 45 minutes it was extremely hard to diagnose
Thank you
I think this is why my Scag Turf Tiger 29hp DFI to cut out.
I haven't check it yet because I just found your video but thank you very much.
I'm sure this helped a lot of people.
Had a faulty tank vent on a BR340, replaced it with an OEM one but was still having fuel starvation issues, installed an Echo one and it hasn't given him any trouble since
My echo srm 210 is having same issue. Starving for air, replaced check valve 3 Times. Still bogs down unless I open gas cap.
Very good job explaining every step of how it operates
Especially at the end... 😄
I pressure test the tanks and fuel lines in chainsaws the same way. I plug my Mighty Vac into the fuel line going to the carb and pump it up to 7#. It better hold. If it holds, I switch it to vacuum and pump it up. It should gradually release. If it does not hold pressure, there could be a leak in the fuel line, tank, tank cap or a bad tank vent. I start looking for the leak with spray soapy water.
smart
Man on man that fresh cut thanks
Or if it dies after a carb rebuild or replacement you can always just unscrew the cap, re prime and try it with the cap off, if it runs fine without the cap then its a vent issue
Yes. KISS method.
Sounded like Jabba the Hut from Star Wars in that blooper.😆😆😆😆
I test my gas tank with my Mighty Vac. I plug it into the fuel line going into the tank. It should pressure up to 7# and hold at that pressure. If it does not pressure up, there is a leak, somewhere. I will use a spray soapy water mixture to find the leak. If a tank does not hold pressure when the gas gets hot it will boil in the tank and cause a lean condition in the saw. After it passes the pressure test, I switch to vacuum and pump it up to 7-10 inches of vacuum. It should gradually reduce to zero inches of vacuum as the tank vent allows outside air in. If the tank vent does not work correctly, the carburator will not be able to pump gas against the vacuum in the tank. You will also hear a “who’s” when you open the gas tank.
I know 👍
Awesome lesson now I know why I have seen fuel leaks where I have thank you sir ! One more step closer to the mower medic 1 small engine diploma
Thank you sir I always struggle wither or not the tank is venting properly always 2nd guessing myself on hand held equipment over this.
Get back to work Rooster Lol
Thanks i never knew thet the tank pressure or vent was important !! Or what acures when its not right !
Got a few old saws that will visibly leak fuel from vent ! Still use them when needed always figured saw isn't quite working right but just put it down to been a old tired machine!! Got to get myself one of them pressure/ vacuum testing gadgets and give the old veterans some tlc
Outstanding advice.
I got brand new FS 91 stihel with a bad vent, back to shop 4 times before they figured it out.
Great video my friend. Very thorough
Had to replace one of these STIHL tank vents , wows expensive. ( EBay )
I pressure cheviot my complete fuel system to 7# and 7inches of vacuum. I pressure check carbs to 5# and 5 inches of vacuum. I check engines to 7# and 7 inches vacuum. The Stihl service manual says they can drop one pound per minute but cannot drop below 4#.
I don’t care with a manual says I want zero leakage
@@THEMOWERMEDIC1 you won’t get it on an ms 440 or 360. You get a gradual leak down to 4#. This is because the oil pump spacer plugs into the pto side seal. Husqvarna has a recess on the 372 where they install a small O ring but Stihl does not and you will get a little pressure loss. I talked with my local Stihl tech and he told me the spec and my 440 passed that spec. He told me not to worry about it. On the 440 the pressure loss is between the spacer’s inside dimension and the crank It does not leak around the seal. I sprayed it good with soapy water and got no leaks. As the saw warms up and the clutch and oil pump are screwed down this little leak probably also stops.
Already replaced carb, air filter, gas lines and filter, but primer still only filing 1 /4, could fuel vent be the issue? Fs40c.
Will it start ok if there's issues with tank vent?
I have an almost new BR800 Stihl backpack blower and when I started it the other day and got to full throttle okay but then after just a few seconds it started to die like it is out of gas. Three or four quick blips of the throttle and it would rev back up but a few seconds later would start to die again. I was sure it wasn’t the gas but dumped it even though it wasn’t that old but it made no difference. It idles fine and I checked several things I was sure it wasn’t and was right so was wondering if you think it may be the fuel tank vent?
Brother thank you I'm having that very problem
Hello, what's the best after market carb for my Stihl FS110 WEEDEATER, thanks for your help and time my friend ! ❤
What pressure/vacuum pump do you use? Could you post a link to it and where to get one, please? Thank you!!
Was just riding my 1996 GL1500 GoldWing. Late night, heading home through a wooded desolate park. Motor was fine and always has been . Just criusing along and withno warning, motor bogged and then died. I pulled over and thought what to do. (Tank was full and I knew it for sure, because I'd filled out last night before garaging. I cranked and wouldn't start but did try Then set full come and it did eventually start. Futzed with throttle and come and got it running again. Staked 5min later. Starting was getting battery drained but got it, drove out of woods. Still thinking "what the hell"? Rinse repeat a few more times. Few miles/ stalls later, I got to gas station. Got carb cleaner and a half gallon of gas to confirm and get fresh. I had begun to think, "what changed and what could I have done when I fuels last night?". "Gas cap? Fuel line? Vent line?". Sure uff, opened fuel door and I had thought looked the vent line. So finished riding home. WOT, anything, didn't have problem going last 8 miles. So, I figured, UA-cam up some vids on the vent line and stallinng. 3rd vid was this and near the end, you confirmed not only the effect of vent line "clogging" but also, that is gotten my 30 miles ok riding since filling track last night.
I've been searching everywhere for this information my 03 tahoe had a evap hose break on it and I couldn't find any information about evaps
I'm hoping you can help me with a Bad Boy Maverick zero turn problem. The fuel line from the tank to the fuel pump will not pick up fuel. But if i remove the line from the fitting and put it down in the tank it will pick up the fuel and start. I have installed a new fuel pump and all new fuel filters. The man that owns this mower told me he had try to remone the fuel line inside the tank and couldn't get it out and may have damaged something there. Any info would be appreciated.
I just picked up a new Stihl tank vent and when applying vacuum, it only holds momentarily the starts slowly dropping pressure???
Gas is coming out my carb like the bellagio fountains in vegas.
Soo I am a little confused because it is not clear what the overall function of this part is supposed to do when it is working?
Allow air
IN or OUT?
Very informative, thanks!
What name of that tool I can find brake bleed but not a pump
Is there model number for that tool
So would it cause my engine to shut off after running for about 10 minutes? Then also make it hard to restart I have to let it sit for a few minutes before I can restart.
Excellent video
You seriously need to do a Dr. Evil.
How do you determine of it is the vent or the fuel cap?
So via the stihl technical it says ti check the valve with gas cap on and the inlet plugged and vacuum pump hooked to return. It says there should be no vacuum build up and should hold pressure. Thats the opposite of what you say in the beginning. Im a little confused.
He did it both ways suction and outlet. Opposite each time.
Is a symptom of a bad valve a LOT of vacuum release when I remove the gas cap? I'm having runnability issues on my FS131 Stihl trimmer and it bogs out, loses power, then its hard to keep running. Opening the gas cap and WHOOSH, TF is that?.. I replaced the spark plug, fuel filter, air filter and just run MotoMix. Should I just replace the valve? I don't have the fancy pressure gauge testy.
Absolutely you are on the right track
@@THEMOWERMEDIC1 dude it worked. That valve was shot and the replacement got it running like a champ.!!.👍🏻🔥🔥
That is a great video, it was helpful thanks
so i’m have a problem with some stihl weed eaters the vents keep going bad, I put a new on on it runs for a few weeks then the vent fails. what might cause that?
Thanks for this information.
great info
I have a John Deere 345 r zero turn . I can’t get fuel into the tank . I have to sit for a min and keep adding gas . It always acts full but I have to keep adding fuel . Do you know why that would occur ? I’ve watched 80 videos and nothing addresses this problem . The mower is off and I have to keep adding gas ? Help , please
pardon my question here, sometimes I'm a little slow. So i'm having issues with my Stihl FS91R like it is starving for gas, at 1st it only did this when the motor got hot, now it will not run longer then 30 seconds. When I remove the gas cap I get woosh of air, believe it is vacuum lock. Don't have compression tester but would this be a sign of tank vent needing replacement.
Thanks for your teaching work.
Tim N
Easy test is to disconnect the vent and try restart
My gravely pro turn 152 gas tanks make a intermittent whistling sound throughout the day when it's hot. Is it the gas caps causing this or is it normal for it to do this?
Normal. Might make
Sure the tank vent in the cap is not partially plugged
@@THEMOWERMEDIC1 ok thanks I'll check that out this evening.
Do you know this issue of a Stihl not wanting to start especially after running for awhile and being stopped for a bit. or when the temperature goes up into the 30's or machine is sitting in the sun. Is this something to do with the vent of fuel circuit? Has something to do with heat and fuel/vapour. usually have to prime it then but that isn't enough. Something that helps is I have to hold throttle while starting.
Yes it’s called static flooding
@@THEMOWERMEDIC1 is it one faulty vent. or does the fuel port need to be changed as well
@@brentkelly5445 check vent. If
Good
Replace carb
All my Stihl machines do this. Every single one. The 4 mix ones (KM131R) are the worst for this. Yes throttle fully open helps.
Sometimes I have to remove the spark plug and manually deflood it. I also keep them in the shade when on site so they stay cool and also, NEVER store upside down! always upright :)
Anyone know how to test it for folks who don’t have one of those pump gauge dohickies?
Would this also work for 2 cycles that vent through gas cap?
Yes same procedure Air in but not out
where do i get one of these black vents can any one help me please thank you
if somone could tell me what valve that is i realy need it please and thank you
Well how about that it works like a diode kinda !
No not quite, a diode requires a minimum of .0127 amps to operate. This is not an electrical part
Thank you for explaining that ,with that learned it is meant to keep atmospheric pressure out of the fuel cell?
AHHHHHHH! I got it!
That’s what I like to hear
Gas tank don’t have one